Modules and compatibility

Fields v1 separates the validation front ends from the small shared core.

Module	Purpose	Scala versions	Main external dependencies
fields-core	Rules, policies, effects, validation containers, paths, errors, and Circe decoder syntax	2.12, 2.13 and 3	Circe is optional
fields-value	Value-carrying Field DSL	2.12, 2.13 and 3	Core only
fields-lens	Reusable lens/policy DSL and path macros	2.12, 2.13 and 3	Core only
fields-cats	Cats Effect, Validated, Chain, Eval, and error-container integration	2.12, 2.13 and 3	Cats Core
fields-zio	ZIO effect and validation helpers	2.12, 2.13 and 3	ZIO 2
fields-zio-blocks-schema	Native ZIO Blocks SchemaError instances and policy-backed schema validation for Value and Lens	2.13 and 3	Fields Core and ZIO Blocks Schema

Add only the front end and integrations your application uses. Transitive dependencies provide core, but depending on core explicitly is useful when its types are part of your public API.

libraryDependencies ++= Seq(
  "io.github.0lejk4" %% "fields-core" % "1.0.0",
  "io.github.0lejk4" %% "fields-value" % "1.0.0",
  "io.github.0lejk4" %% "fields-lens" % "1.0.0",
  "io.github.0lejk4" %% "fields-cats" % "1.0.0",   // optional
  "io.github.0lejk4" %% "fields-zio" % "1.0.0",    // optional
  "io.github.0lejk4" %% "fields-zio-blocks-schema" % "1.0.0", // optional integration, Scala 2.13/3
)

Choosing a front end

• Choose Value when validation is local and direct access to the current value/path makes rules easiest to write.
• Choose Lens when policies should be reusable without wrapping the validated model in Field values.

Both use the same core RuleK, PolicyK, Effect, Validated, path, and error concepts.